The goal of this work is to develop antibodies to differentiation antigens found on cultured human lymphoblastoid cells. Three cell lines, derived from two patients with acute lymphoblastic leukemia (ALL), were chosen as immunogens. Two of the lines, RPMI8392 and RPMI 8402, were derived from the same patient and are, therefore, autochthonous cell lines. RPMI 8402 cells are T lymphoblasts that emerged from the leukemic stemline, while RPMI 8392 cells are immunoglobulin-producing, Epstein-Barr viral genome-containing B lymphoblasts that arose from the patient's residual normal B cells. The third cell line, NALL-1, arose from the blood of a 14 year old boy with non-T, non-B cell ALL. These cells produce terminal deoxynucleotidyl transferase (TdT) and bear both the Ia and common ALL antigens. Cultured NALL-1 cells do not produce immunoglobulin nor do they form E rosettes. Thus, NALL-1 cells are phenotypically very similar to "common" ALL cells. The purpose of our project is to generate antibodies to T, B, and lymphoid stem/progenitor cell surface differentiation antigens that are found on these cells. Our plans include the generation of antisera in rabbits to each cell line. We seek the class of antibodies that binds only to one of the two cell lines. These antisera are being analyzed to define specificities against a range of differentiation antigens found on mature, differentiating and neoplastic lymphoid and hematopoietic cells.